RU2367974C2 - Method for detection of non-radial projection of moving target speed - Google Patents

Abstract

FIELD: physics, measurement.

SUBSTANCE: invention is related to radio engineering, namely to radio location methods for detection of moving object speed. Substance of invention consists in the fact that target is radiated with probing signals with frequencies f1 and f2 distanced in space by transmitting antennas, difference of received signals frequencies is defined, and using calculating expressions, projection of target speed is identified to direction of non-radial vector. Invention may be used both in radio location and in police meters of vehicle speed.

EFFECT: provision of possibility to define non-radial speeds of target, which makes it possible to definitely determine both value and direction of vector speed.

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Description

The invention relates to radio engineering, and in particular to radar methods for determining the speed of a moving object, and can be used in radar, to predict the position of a moving target or to select moving targets. In addition, the invention can be used in police car speed meters.

A known method for determining the radial velocity of a two-frequency radar station {Bakulev P.A., Stepin V.M. Methods and devices for moving targets selection. M .: Radio and communications, 1986. - 63 p.}. This method is based on the generation, modulation and emission of time-aligned radio pulses with the same repetition period at the carrier frequencies f ₁ and f ₂ , the simultaneous conversion of these radio pulses into a reference coherent signal of a difference frequency Δf = f ₁ -f ₂ , receiving frequency signals reflected from the target f _c1 and f _c2 , converting the reflected signals into a differential frequency signal Δf _c = f _c1 -f _c2 and determining the frequency difference between the converted and reference signals (Δf _c -Δf), which is proportional to the radial projection of the target speed.

However, the known method allows you to determine only the radial projection of the velocity vector of the target. In this case, both the direction and the absolute value of the velocity vector are determined ambiguously.

In the case of a plane motion of the target, to uniquely determine the velocity vector, it is necessary to specify two of its projections on two different directions. If one of the projections is radial, then the other should be non-radial, that is, a projection in any other direction.

In the three-dimensional motion of the target, to uniquely determine the total velocity vector of the target, it is necessary to determine its three independent projections. If one of these projections is radial, then the other two should be projections into two other directions.

Thus, in the case of plane motion of the target, and in the general case, for the unambiguous determination of the velocity vector, it is necessary to determine the non-radial projections of the velocity vector.

The invention is aimed at solving the problem of determining the non-radial projection of the target’s speed, which can be used to uniquely determine the velocity vector.

This technical problem is solved as follows.

Using two transmitting antennas located at different points in space, the moving target is irradiated by two time-aligned sounding signals with carrier frequencies f ₁ and f ₂ , signals reflected from the target with frequencies f _{signal 1} and f _{signal 2} are received by the receiver, the frequency difference Δf _signal = f _signal1 -f _signal2 ,

the value of V _D is determined by the formula:

where c is the speed of light;

и

- единичные векторы, направленные на цель из точек расположения соответственно первой и второй передающих антенн;

and

- unit vectors aimed at the target from the points of location of the first and second transmitting antennas, respectively;

- единичный вектор, направленный на цель из точки расположения приемной антенны. Если в качестве приемной антенны используется антенна, излучающая зондирующий сигнал частоты f₁ или антенна, излучающая зондирующий сигнал частоты f₂, то

или

соответственно;

- a unit vector aimed at the target from the location of the receiving antenna. If an antenna emitting a sounding signal of frequency f ₁ or an antenna emitting a sounding signal of frequency f _{2 is} used as a receiving antenna, then

or

respectively;

V _D is the projection of the target velocity V on the direction of the vector D, determined by the formula:

.

.

The drawing shows a vector diagram illustrating the use of the proposed as an invention of the method. The designations in the drawing correspond to:

A ₁ - transmitting antenna emitting a sounding signal of frequency f ₁ ;

And ₂ is a transmitting antenna emitting a sounding signal of frequency f ₂ ;

And _pr is the receiving antenna;

C is the goal;

r ₁ , r ₂ - vectors, the beginnings of which are at the locations of the antennas A ₁ and A ₂ , and the ends - at the location of the target;

r _ol - a vector whose beginning is at the location of the receiving antenna A _ol , and the end is at the location of the target;

,

,

- орты векторов

,

,

- unit vectors

r _1, r _2, r _pr.

The instantaneous values of the phases Ψ ₁ (t) and Ψ ₂ (t) reflected from the target of the signals depend on the distances r ₁ and r ₂ from the respective transmitting antennas to the target, as well as on the distance r _pr from the target to the receiving antenna:

where ψ ₀₁ and ψ ₀₂ are the initial phases of the probing signals of frequencies f ₁ and f ₂ .

We differentiate these expressions in a complete way with respect to time, taking into account that when the target moves, the values of r ₁ , r ₂ and r _pr depend on time.

Subtract these expressions from each other, while taking into account that

- скорость цели.

- target speed.

Then

We introduce the notation:

.

.

Reducing by 2π and grouping the terms, we get:

, где D⁰ - орт вектора D.

where D ⁰ is the unit vector of D.

We take into account that VD ⁰ is the projection of the vector V onto the direction of the vector D.

Denoting this projection as V _D , we obtain:

The frequency values f ₁ and f ₂ or their difference can be known in advance or measured with sufficient accuracy. The accuracy of determining the value (f ₁ -f ₂ ) can be improved by measuring directly the frequency difference. For example, the signals of frequencies f ₁ and f ₂ can be converted into a difference frequency signal with subsequent measurement of this frequency. It is possible to use other methods of measuring the frequency difference of the probing signals.

The value of Δf _signal = f _signal1 -f _signal2 can be determined by measuring the frequencies of the received signals with the subsequent calculation of their difference. However, to improve the accuracy of determining the value of Δf _Sig expedient to convert received signals of frequencies f and f _{ACT1 sign2} a difference frequency signal, and then measuring the frequency transformed signal.

From the vector diagram in the drawing it can be seen that the direction of the vector D does not coincide with the direction from the location of the receiving antenna to the location of the target, that is, the vector D is not radial.

Claims (1)

The method for determining the non-radial projection of the target speed, which consists in the fact that the target is simultaneously irradiated with two sounding signals of different frequencies, the signals reflected by the target are received and the frequency difference of the received signals is determined, characterized in that the target is irradiated with sounding signals by transmitting antennas spaced apart in space and by the formula

determine the projection of the target’s speed on the direction of the vector D, determined by the formula

,
where c is the speed of light;
f ₁ and f ₂ are the frequencies of the first and second sounding signals;
Δf _signal = f _signal1 -f _signal2 is the frequency difference of the received signals;

and

- unit vectors aimed at the target from the points of location of the first and second transmitting antennas, respectively;

- a unit vector aimed at the target from the location of the receiving antenna.

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